The present invention relates to the general technical field of agricultural machinery. The invention relates to a distribution machine with a supply device for a self-regulated pneumatic supply from a main reservoir containing product toward at least one auxiliary reservoir according to its filling rate via a respective tight duct, each auxiliary reservoir comprising an air exhaust device and a distribution unit for distributing the product comprising a supply chamber and a rotary regulating element.
Such a supply device for a seeder is described in application FR 2 315 834. This supply device makes it possible to convey product, such as seeds, from a main reservoir to at least one auxiliary reservoir. The product is conveyed via an air flow through a tight duct according to the filling rate of the auxiliary reservoir. The auxiliary reservoir has an air exhaust device implemented on one of its sidewalls. The air exhaust device creates a loss of charge that decreases according to the filling of the auxiliary reservoir. When the auxiliary reservoir is full, the loss of charge is nil and the conveying of seeds from the main reservoir is stopped. The auxiliary reservoirs are therefore supplied with seeds individually and automatically according to their filling rate. The supply of the auxiliary reservoir via an air leak depends on the type of product that is conveyed, and in particular on its shape and capacity to obstruct the air exhaust device.
Another self-regulated pneumatic supply device for a distribution machine such as a seeder is disclosed by document WO 2011/002541. The seeds are conveyed through a tight duct from the main reservoir to the auxiliary reservoirs. The end of the duct is provided with air exhaust openings and is placed above the distribution unit. When the seeds accumulate substantially above the air exhaust openings, the seed reserve reaches a high level. The supply of seeds is then interrupted, since the air flow no longer manages to pass through the seeds. The seed level decreases as the rotary regulating element delivers the seeds into the soil. When the seeds have reached a low level below the openings, the air flow increases and the conveying of seeds resumes and continues until the high level is once again reached. The openings of the air exhaust device extend above the distribution unit, and as a result the maximum level of the seeds is higher than the seed overflow spot in the distribution unit. The seeds contained in the auxiliary reservoir supply the rotary regulating element and tend to “push” the seeds from the supply chamber so that the seed level is at the same height in the distribution unit. This phenomenon may cause the seed layer to rise up to overflowing and release seeds in addition to those picked up by the rotary regulating element. The seeding quality is therefore altered by releasing a volume of seeds instead of a regular single seed regulation. Furthermore, the beginning of conveying seeds to the auxiliary reservoir, nearly emptied of seeds, often takes place in an uncertain manner due to an insufficient air leak at the auxiliary reservoir. In that case, the rotary regulating element risks rotating without seeds.